The present invention relates to optical articles, in particular ophthalmic lenses, especially for eyeglass lenses, comprising an anti-reflecting coating which also imparts to the articles anti-fogging properties even when the optical articles are provided with an anti-soiling coating (top coat).
1. Field of the Invention
In the ophthalmic optics field, ophthalmic lenses are traditionally provided with various coatings so as to give these lenses a plurality of mechanical and/or optical properties. Successive coating layers are thus traditionally formed onto an ophthalmic lens, such as impact-resistant coating layers, abrasion and/or scratch resistant coating layers (hard coatings), anti-reflecting coating layers (AR coatings), antistatic coating layers and anti-soiling coating layers (top coats).
As defined hereunder, an AR coating means a coating that has been deposited onto the surface of an optical article, which does improve the antireflective properties of the optical end product. It makes it possible to reduce the light reflection at the article-air interface area within a relatively large portion of the visible light spectrum.
More precisely, an AR coating provides a Rv of 2.5% or less (per face of a coated lens). The mean reflectance factor Rv is such as defined in ISO standard 13666:1998 and measured in accordance with ISO standard 8980-4, i.e. it is the balanced average spectral reflection in the visible spectrum in the wavelengths limits ranging from 380 nm to 780 nm.
Fogging of ophthalmic lenses is troublesome for the wearer, and can be unsafe as it will reduce wearer's vision and even in some cases “blind” him.
Fogging will occur when the temperature of the lens is lower than that of its environment. Then, humidity contained within the air surrounding the lens will condense on the colder surface of the lens.
2. Description of Related Art
Different solutions for reducing the fogging propensity of ophthalmic lenses are commercially available.
A first solution is the use of an anti-fogging temporary solution, generally comprising poly(oxyalkylene) surfactants. Temporary solutions have to be applied frequently on the lens surfaces and their efficiency is highly questionable, especially in the case of lenses provided with an anti-soiling coating.
JP2004-317539 describes a process for preparing an optical article, especially a lens having antifogging properties which comprises treating a base article with a treatment agent comprising a hydrophobic part containing fluorine atoms, a hydrophilic part comprising a polyoxyethylene group and a coupling unit, such as an alkoxysilane, that reacts with the surface of the article to form an article whose surface has a contact angle with water from 50 to 90°. This article is then treated by a surfactant having a HLB value from 5 to 15 in order to get an antifogging layer.
A second solution is the use of anti-abrasion coatings having anti-fogging properties. The drawback of this solution is that these coatings are very soft and leads to easily soiled lenses, with generally poor abrasion resistance. They have no antireflective properties.